I'm sure this is a common problem, and I did look for a similar post elsewhere, but I couldn't find the exact situation, so I'm now asking for some guidance.

As a cost saver, I've always kept my hot water heater set at a relatively modest setting, but about two days ago, the hot water started coming out scaldingly hot.

I removed the plate of the now 9 year old State water heater (never any problems up to this point) and checked the thermostat: no gremlins had changed the setting. I backed it off the "hot side" just a touch, but no change. Still dangerously hot.

Finally, today, no hot water. Assuming the extremely hot water had tripped the regulator, I punched the reset button, hoping the water would soon be back to its normal temperature.

Soon after, the hot water was back, but unfortunately, it's once again of the scalding variety.

I know this must be "Plumbing 101", but is this an indication I need a new thermostat or what?

I'm also embarrassed to say I've never done any maintenance on the water heater, such as draining and flushing. Could that have any thing to do with it? (And since most of you monitoring this board are likely professionals, I promise to have one of your brethren over soon to perform the proper maintenance.)